If you want a do everything bike (mass start, sprints, pursuits) either 170 or 172.5.

If you are going to focus on pursuits, 175. Past that trial and error. I ride 175 on my road bike, and have used 170, 172.5 and 175 on track bikes, I've really leaned to 175 across everything these days.

I'm sure the sprinters will all chime in, in a sec and say go tiny, 150mm or you're soft ;p

Anything over 170mm is uncommon (but not unheard of) on the track, just like anything over 175mm is uncommon (but not unheard of) for road riding.

165mm used to be the "sprinters crank length" back when sprinting was done with really high cadences on normal gears (90-94 gear inches). I read an interview where Marty Nothstein at 6'2" rode 165mm cranks. Now sprinting is done on gears in the high 90s and into the 100 gear inches using lower cadences, so some are going with longer crank arms because some want more leverage for the bigger gears. In years past, flying 200M average cadences were in the high 150s-160s. Now they are in the 130s-140s but using much bigger gears.

Note the cadence differences during the final sprints of these World Championship matches 17 years apart:
1994:

2011:

Other generalizations:
- Sprinters/spinners choose shorter than normal crank lengths in order to facilitate higher than normal track racing cadences and max speeds
- Pursuiters choose longer than normal crank lengths in order to get more leverage to roll bigger gears and don't have to worry about speed changes (as in a points race).

On a personal note:
I'm 6'1" and ride a 57/58cm bike (road and track). A 57/58cm road bike would have 175mm cranks and a 57/58cm track bike would come with 170mm cranks. But, I prefer a higher than normal cadence on the road and I often reach high RPMs on the track (when I'm lucky), so I use 170mm on the road bike and 167.5 on the track.

Just like Bob above, some people run the same crank length on their road and track bikes to keep the same feel. I'm tempted to do this myself, especially being that my road bike setup like a track bike with gears and brakes (low bars, forward saddle, etc...). My road bike is not setup for comfort at all. Any ride over 1.5-2 hours is tough on my arms and back.

So, what do you expect people should be targeting for a cadence in a standard pace line, and for sprinting (i.e. in a points race)?

Pacelines are dependent on a lot of things. But, what I've learned is that as one progresses through the ranks, cadence ranges generally stay the same, but gearing goes up. I would say that the cadences in a points race are:
Pacelines: 100-120 RPM
Sprints: 120-140 RPM

A beginner racer would use like a 88-90" gear in such a race. An elite racer might choose 94-99" depending on their riding style.

Disclaimer: This is just from my personal experience and from what I've learned by watching others around me. There are lots of factors that go into this, like for example: Track geo (333M vs 250M, 25 deg vs 44 deg), track surface (Siberian Pine vs concrete). Plus, I'm not much of a points race guy. There are others that know more than me (Paging: Biting Duck).

Points races usually arent the best to gauge any sort of standars. More so than most races they break up into seperate groups with people off the front and the back. If there is a good sized group chasing a person or two the pacing may be 90% of a sprint lap, but if most of the field is together, or not wanting to chase it could drop to 60%. And if you are off the front or the back it can vary greatly.

I'm a points guy, I'd say I probably tap out about 100RPM, probably only max out about 120-130RPM in a sprint (55-58km/h), pushing generally either 96 or 98 inches. While Kayce is right to some extent, you do find large segments of races that do hang together, where you're sitting on a pretty quick speed, with accelerations on the sprint laps obviously.

I think the standard used to be to go shorter than road setup, and I think this is still very common amongst the guys doing lots of sprint events, but for a lot of mass start riders (ex Kierin) I've seen the lengths creep up over the past 10 years. Same with pursuit, where I'm seeing guys synch with their TT type setups, which are a bit longer (I ride 180mm on my TT setup). If I ever get round to a season focusing on pursuit (rather than a side line, I'll go longer than 175).

My own stats I'm 6'2", 57.5 effective TT (58mm on my road bikes), about the quickest I ride is in scratch races, where I'll hit around 62-63km/h in the sprint. It's one of those things where over time you'll find out what works best for you and what doesn't same with pretty much every other setup aspect on a bike.

I started track racing after a long road career on 170's. While now I'd prefer not to ride that short, I don't think they held me back any.